General Chain Design Considerations

This section reviews the general considerations for the design of roller, silent, engineering steel, and flat-top chains. The considerations differ as the functions of each type of chain differ. The specific design considerations for each class of chain will be covaed later. 

The following discussions are very brief, as a thorough discussion of these factors is beyond the scope of this book. This chapter is only intended to acquaint the reader with the factors that chain designers must consider. It does not try to teach the reader how to design chains. 

Shock loads are caused by the characteristics of the power source and the driven machinery. They occur repeatedly in a regular cycle, usually one or more times in each shaft revolution. They usually must be added to the nominal tensile load. Service factors are used to account for commonly known shock loads in most chain drives and conveyors. 

FIGURE 3-1 How the tension varies in a chain that is 100 pitches long as it runs around 20-tooth sprockets. Inertia Load 

As the term is used here, inertia loads are different from shock loads. Inertia loads are the occasional loads imposed on the chain by imusual, and often unexpected, events. They may come from starting a heavily loaded conveyor or a drive with a large flywheel. Or they may be caused by a sudden momentary jam in the driven machine or conveyor. The drive or conveyor designer should calculate expected starting loads and be sme that they are never more than the yield strength of the chain. 

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Performance In general, a service performs more poorly than an in-process method call due to network latency and bandwidth constraints. To make things worse, a service may call other services to fulfill its responsibilities—a chain of services. Performance has to be a design consideration throughout the development cycle. 

Hat-top chains are used almost exclusively on eonveyors. In praetiee, the flat-top chains covered here are basically special types of slat conveyors. Hat-top ehain eonveyor speeds are generally less than 300 ft./min and the maximum chain pull is usually much less than 1000 lb. The major design considerations for flat-top chains to be used in conveyors are several of the tensile loads, several types of wear, lubiieation, and environment. 

In order to carry out most biochemical reactions, metalloenzymes generally utilize the rarer transition metal ions. Elements such as zinc, copper, iron, nickel, and cobalt are found in low concentrations in plasma and seawater and yet the enzyme has to select the appropriate metal ion from them. There is evidence for the existence of proteins that can chaperone specific metal ions to their appropriate sites in apoenzymes, protecting the metal ions from adverse reactions as they are guided to their required location [5]. How does the enzyme attempt to select out the one metal ion it requires The answer is that the chemistry of the metal ion is used as a basis for selection. Each metal ion has some property that is different from that of most others, but, in fact, there is often considerable overlap in these properties so that a given enzyme may bind one of several different cations in one specific site. Some relevant data are provided in Tables 1 and 2. The metalloenzyme contains within its overall design an arrangement of preferred side-chain functional groups with the correct size hole to bind the required metal ions in an appropriate hydrophobic or hydrophilic environment. Thus the metalloenzyme binds metal ions... 

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